Conventionally, portable electronic devices such as cameras and the like have used lithium batteries, alkali batteries or the like as power supplies. However, compact fuel cells have been proposed as the next generation of power supplies.
Besides using methanol, fuel cells use oxygen in the air as fuel.
However, in cases where a fuel cell is used as the power supply of a camera, the use time is limited by the amount of oxygen that is present inside the housing of the camera, so that the camera cannot be used for a long period of time.
On the other hand, in the case of an electronic device using a lithium battery, alkali batter or the like, the state of the battery can be determined by detecting the output voltage of the battery.
However, in the case of small fuel cells with a long useful life for which use in portable electronic devices or the like is envisioned, if only the output voltage of the cell is detected, the following problem arises: namely, in regard to the state of the cell, it cannot be determined whether there is no fuel (e. g., a fuel such as methanol or the like) remaining in the fuel cell, whether the oxygen is insufficient, or whether there is an abnormality in the cell parts.